A novel ozone source was developed to study the negative ion chemistry of ozone in the gas phase. Rate constants and product ion branching fractions are reported for 17 negative ion-molecule reactions involving ozone (O-3). This is the most comprehensive set of O-3 reactions with negative ions to date. The reactions proceed primarily through charge transfer and O atom transfer. The reaction rate constants for O-, O-2(-), and OH- are large and approximately equal to the thermal energy capture rate constant given by the Su-Chesnavich equation based on average dipole orientation theory. The negative ions NO2-, CO4-, SF6-, and PO2- are somewhat less reactive, reacting at approximately 20-50% of the thermal capture rate. The hydrofluorocarbon ions CF3- and C2F5- react at 80% of the thermal capture rate, and F- is the major product ion formed. NO3-, CO3-, PO3-, CF3O-, F-, Cl-, and Br- are found to be unreactive with rate constants < 5 x 10(-12) cm(3) s(-1), which is the present detection limit of our apparatus using this ozone source. The I- ion was observed to cluster with O-3 to form IO3- with a rate constant of approximately 1 x 10(-11) cm(3) s(-1), which is a factor of 2 above our detection limit, and no other product channels were observed. All of the anions listed above showed no reactivity, k < 5 x 10(-13) cm(3) s(-1), with O-2.